Character identification and microscopic identification was used to study the pharmacognostical histology of P. japonicum. The results showed as follows. In cross section of the roots, nearly square or oblong stone cells were mingled with the cork layer of root. The cortex and phloem had vittas ranked in a ring; cylindrical stem showed 25～40 longitudinal ridges, and the inside of ridges contained collenchyma and vitas. The vascular bundle situated in the inside of ridges was more developed; the leaf was isolateral; vittas were obviously discovered above and below the vascular bundles and in the phloem, and its parenchyma cells contained aurantiamarin crystals which were radial or needle cluster. Those features of pharmacognostical histology are stable, dependable and can serve as one of references for the identification of P. japonicum.